tamerlan taught everything to himself. >> reporter: the fbi wants to question tamerlan's wife, who is described as a smart young woman who grew up christian, but converted to islam, after meeting her future husband. she now has an attorney who is negotiating with the fbi over how that interview will take place. >>> across boston, a moment of silence was observed today for those who were maimed or killed one week ago. silence fell over the city at exactly 2:50, marking the moments when the bombs went off, 11 seconds apart. memorials were also held along the marathon route and on the very spot where the bombs went off. during the observance people stopped citywide to reflect and remember. later, the fbi turned the crime scene back over to the city of boston. ♪ [ music ] a police honor guard lowered the flag that had flown at the finish line of the marathon, and presented it to the mayor. a six block area had been cordoned off a as crime scene. boston officials say they need to assure they assess the structural integrity of the area as well as conduct the cleanup before they open the a